Hi @Megderoyale,
Can I ask if a particular message or error code displays on the screen when you're trying to link to ATO online services? Or are you having issues answering the questions specific to you?
There are a few reasons why you might not be able to re-link ATO to a new myGov account.
For example, if you're trying to us the same email address you registered to your original myGov account, you need to speak with the myGov helpdesk to remove it from your old account so you can use it again (once an email address is registered, it can't be used again unless it's unlocked).
If this is possibly what's happened, you could also try registering a different email address and seeing if that works?
You can also use the troubleshooting page for myGov from here.